Method of making magnetic recording heads



Oct. 7, 1952 M. CAMRAS 2,612,681

METHOD OF MAKING MAGNETIC RECORDING HEADS Original Filed Nov. 29. 1945 Fay-.1

Fz a! F? .E a' 7 7 2 l l E i-/9 72 i g I E I l9 l 2/ fnys'nfmr' Patented Oct. 7, 1952 Q 11 METHODOF Marvin Camras,

. Original.application-November N0. 631,682,n0w.,1 atent .-No. 2,4 56,767 dated;

December 21,1948, Divided andthis applica ticn February 17,1947, Serial No.,,7;2 9,1,00.

suited for use with a wire orothenelongated recording medium which islongitudinally mag;

netized. I j

This application is a division of my copendiiig application for patent entitled Magnetic Record ing and Reproducing Head, U. S. Serial No.

631,682, filed November 29, 1945, issued now as Patent No. 2,456,767, and assigned to the same assignee as the present invention'. v

In magnetic recording and reproducing devices, it has been found very desirable to, have a head 2,612,681 V MAKING'MAGNETIO i REGQRDING=HEADS v I SQhicagc, Ill., assignor to Armour Research, Foundation of Illinois'jInstitute 'of ecli'nol'ogy Chicago, nus corporation of Illi.-,

2 9, 1945, Serial.

acteristieof myinvention' are set forth in Particularity in the appended claim. My invention itself, howevenbbth, as to its "organization and method. of making tog 'ether with further objects and advantages thereof maybest be understood by reference to theiollowing description taken in in which a single core piece" comprises the core for the erasing coil, for the signal coil, and for the coil which supplies the highfrequency component to the non-magnetic gap associated with the signal coil during the recording operation:

It has also been founddesira'ble that such. an electro-magnetic transducer head should be of the so-called open slot type-whereby'an' elongated record medium does not have to betlir'ea'ded through any of thecoils. When magnetimmaterial having a relatively high coercive for-ceis used for the elongated record medium, considerable difliculty has been experienced in the past in properly and adequately erasing the previous history on the record medium, Difficulty has also been experienced during'reproductionawhere a common core structure is used for both the erasing coil and for the signal coil, since the stray flux created in the core by the record medium crossing the erase gap sets up an out of phase flux which threads the signal coil. This out of phase flux represents distortion of the voltage induced in the signal coil.

One of the principal features and objects of the present invention is to provide a novel method for making an electro-magnetic transducer head which overcomes the difliculties previously experienced. l

A further object Of the present invention is to provide an extremely economical method of manufacturing electro-magnetic transducer heads of high quality.

Another and further object of the present invention is to provide a novel metal working process.

Still a further object of the present invention is to provide a novel core structure for an electromagnetic transducer head and to a novel method of assembling coils thereon.

The novel features which I believe to be charconjunction with the. a companying drawing; in which: l

- Figure, 1, ,fisiianj elevational view of thef core member of an electromagnetic transducer head embodying the novel'teachingsand p ipl es of the present inv'ention;j 1 Figure .2' is an; l ,Iv'ationa1 vieW I OfYthe core shown in Figure '1' 'with' the eras'efcoil, signal'coil andhigh frequency coil mountedfthereony; Figure 3 is a'n end view ofl t he assembly shown in Figure 21 1 1 1 Figure 4 is an elevational-view of the'eras'e coil spool; c c I 1 Figure 5 is atopview of theerase coilsp'ool; Figure 6 is an. elevational view ,of-the signal 01 sp o d: Figure 7 is a top. view of the signal coil spool. .Referring; first ,to :Figure 1 ofv the drawing, there is illustrated-thereinacore ,llj for an electro-mag'netic .transducenyhead.-= This core H is in the form of a'flat plate or stamping. having a base portion 12,: a central. T-shapedjleg i3 and 1 tWO outer legs"l'4and-"l5. Thedeg 'lijis someaccommodate a'signalcoil" I1 asweu as a high frequency coil [8 while the leg I4 only accommodates an erase coil H5. The core H may be formed of any suitable magnetic core material having a relatively high initial permeability, relatively low coercive force and having a saturation level somewhat higher than the record medium with which the head is to be used. By way of example, and not by way of limitation, this core piece may be approximately .20 inch thick andapproximately three-quarters of an inch high.

In Figure 2 of thedrawing, the erase 0011 it, the signal coil IT and the high frequency coil l8 are shown mounted on the core. The erase coil 16 is mounted on the leg [4 while the signal coil l1 and the'high frequency coil l8 are mounted on the leg [5. While the high frequency coil is shown as being disposed below the signal coil I1, its relative position on the leg l5 may be reversed if desired.

The erase coil It may be conveniently wound on a spool l9 such as shown in Figures 4 and 5 of the drawing, the spool [9 having a central opening 20 to enable it to be slipped over the leg M in a manner presently to be described. Similarly, the signal coil may be conveniently wound on a spool Zl asma beseen in Figures 6 and 7 of the draws the 2 1 i itl a central opening 22 to enable itto beslipped over the leg IS.

The above referred to structure enables a very eocnomical production of the e1eCl3rQ-;mag ne t1 transducer headsince the erase coil I6 a m I signal coil I! may be wound in advance on their respective spools l9 and 2| mastectom spool While I haiie shown and describ embodiment of my inventiom'it W111, be understood thatI do not wish to be limited by way of limitation, the frequency of this source may be of the general order of magnitude of twenty to fifty kilocycles p er second of course,

thereto, since many modifications may be made,

winding machine. To assembleiitheooilsjonthe core II, the legs l4 and I5 are'loent'oii't' of the plane of the leg l3 sumcient to enable the spools i9 and 2| to be slipped over their respective legs;

The legs l4 and [5 are then'bentbaelsjnto os tion so that they lie in thesameflplanes -a'sithe central leg I3 and the gaps are checked'andad justed with a thickness gauge. At thistime, a; drop of solder or other -non-magnetic binder is preferably dropped into the-gaps. and 24,. The solder dropped into theigaps 2.3 and 244. not only serves to hold the legs in .a position where their gaps are fixed and determined, but also. serves tokeep dust and other foreign particles out. of thegaps. W I v The upper edgeshilthelees l4. .l3'land 'lti'are slotted lengthwise of the edge as at 25 torec'eive a wire or thread-like record medium. 7 I 1 The high frequencyicoil 18 is formed by simply and ,I therefore contemplate by the appended ciaim-to cover all such modifications as fall within the true spirit and scope of my invention.

"t" Islaim as my invention:

.Ql'The method of making an electro-magnetic "transducer head'for transducing signal energy between a traveling magnetic record medium and ian electric circuit comprising the steps of stamping from paramagnetic sheet material three parallel straightlegs integrally joined at one of their ends and free at their other ends with a T-shaped retaining head on the free end of the winding afew turns'ofthelead wire to the erase coil 1 B'around the leg [5 in such ,a direction as to oppose the stray flux from the eras'egap; This is preferably done beforefthe'si nal coil ll] has been dropped into. place. II 1 I j I The signal coil v T has its opposite ends connected through conductors 26 and 21 to the maincircuit of the magneticrecorder' and reproducer (not shown) I The lowerend of the erase coil [6 is connected through a conductor 28 to one side of a; suitable center leg, bending the free ends of the outer legs out of theplane of the center leglto separate the free ends. of the legs. at least. a distanceequal tothe original parallel spacing of'theleg contemnoraneously slipping a tightly fitting. preformed coil on each of the outer legs, and bending the outer legsback to the plane of the center leg to a predetermined spacing from the T Sha'ped head to retain each coil snugly onits respective le I a I a.

i MARYIIN'CAMBASL examinations CITED The following references are ofreord in 'the file of this patent: v 

